1. Field of the Invention
The present invention relates to a motor housing of a brushless motor, and more particularly to a brushless motor having a motor housing molded by plastics mixed with magnetic materials.
2. Description of the Related Art
In a brushless motor of face opposed flat type structure, small sized precision motors such as DC motors, Hall motors or seat coil motors are comparatively prevalent, and they are widely used as driving sources of the various electronic apparatuses.
In this motor of the face opposed flat type structure, it is required to decrease thickness of the motor to the extremity to get a thin type motor.
However, as for these types of brushless motors with face opposed flat type structure generally, a motor shaft is movably supported at the boss portion of the motor housing, and to the end of which (flange face) a stator yoke and an exciting coil are installed and a rotor yoke and a rotor magnet are installed on the rotor fixed to the motor shaft to obtain torque by the magnetic circuit formed through them.
By the way, it has conventionally been adopted a structure, wherein the aforementioned stator yoke is generally made with the parts of magnetic materials independently to fix to a motor housing which is molded by non-magnetic materials such as plastics or is a cutting product made of magnetic and non-magnetic materials.
However, in such a conventional brushless motor, some problems have been observed such that another stator yoke has been required, the number of the parts to be used has been increased, and the increase of the number of assembly has led to the increase of the assembly man-hour. Therefore, a brushless in a form of both a rotor and a stator serving as a housing has been disclosed as Japanese Laid-Open Patent Application No. Sho 60-174053.
But, in such a case, a stator yoke is formed by electric conductors such as iron to advantageously attain high magnetic flux density, but in some cases, increasing the rotation speed (exciting frequencies) causes eddy-current loss sharply.